Process of beneficiating langbeinite ores



United States Patent 3,016,138 PROCESS OF BENEFKiIfigIING LANGBEINITE The present invention relates to a process of beneficiating or concentrating langbeinite ores. More particularly, the process of the present invention relates to the beneficiating or concentrating of potash ores of the mixed type, that is, potash ores containing langbeinite sylvite (K Cl), and halite (NaCl), as principal constituents, using a spiral separation operation.

As is well known, potash is of great economic impor* tance. The sources of potash are very numerous. Extensive deposits of potash salts are found on every continent; however, in practically no instance is the potash salt found as a substantially pure salt. On the North American continent, one frequently encountered potash salt is sylvi-te. The sylvite is not often found in any appreciable quantities as pure sylvite ore, but is most found as the sylvinite ore, which is a mixture of K01 and NaCl. -Sylvinite ores sometimes have a high purity of approximately 96%, and a typical analysis of such an oreis'as follows:

" W Percent Sylvite (KCl); 31

Halite (NaCl) L.. 65 Other constituents or impurities consisting of silicates,

sulfates, etc 4 The sylvite values of ores of such a high purity may readily be recovered or concentrated byvarious concentration processes, such as crystallization, flotation separation, etc.

Langbeinite ores, specifically mixed ores containing langbeinite, sylvite, and halite, are more difiicult to upgrade using conventional pro'cesses. A typical analysis of such an' ore is as follows:

. f Percent Sylvite (KCl) 10.6 Halite (NaOl) 53.2 Langbeinite (K SO .2MgSO 33.9 Other .constituents or impurities a 2.3

Accordingly, it is an object of the present invention to provide'a process for beneficiating a potash ore containing langbeinite.

3,016,138 Patented Jan. 9, 1962 to comrninute the ore to liberate substantially all of the constituents; however, the ore may be liberated to a lesser extent, for example, to 70-80% liberation. This granular material is sized to produce a granular feed of a particle size of about 5 mesh and preferably a feed consisting of 8 +100 mesh particles, and still more preferably a feed consisting of -l4 +48 mesh particles. The comminution of the ore may be carried out in a ball mill, roller mill, hammer mill, or any other suitable type of grinding or crushing apparatus. When the ore is ground to the mesh size indicated above, the langbeinite values, the sylvite values, and the halite values are substantially completely separated from each other and the ore is ready for further treatment in accordance with this invention. a

The comminuted and sized ore is then pulped with brine to form a slurry of from about 20% toabout 40% solids concentration. The pulp in slurry form is allowed 'to proceed by gravity in a downward spiralling path at a rate of flow at least sufiicient to avoid any substantial amount of agglomeration of particles. The spiral pathwaythrough which this feed is processed is formed by means of a'trou gh constructed of any suit-able material such as wood; metal, plastic,- etc.; and although no specific number of turns to the spiral for the slope of the trough' is required, it has been found that a suitable It is another object of the present invention to 'provide a process for beneficiating a potash ore containing langbeinite to obtain a concentrate of increased langbeinite concentratiom It is a further object of the present invention to provide a process for beneficiating a potash ore containing lang beinite, sylvite, and halite.

These and other objects and advantages of the present invention will be apparent to those skilled in the art as the description of the present invention progresses.

In accordance with the present invention, it has been discovered that eminently satisfactory be neficiation of potash ores and minerals containing langbeinite can be achieved through spiral separation nethcds by means of a series of critical and interdependent process steps. Generally described, a potash ore containing langbeinite is first comminuted to economical liberation size to produce a granular feed material. The comminution of the ore to the liberation of the various constituents to be sep arated is effected to liberate a substantial amount of the spiral pathway comprises a spiraltrough, 6 feet'high, having five turns in the spiral. The outside diameter of curvatureof the'spiral is about 24 inches, while the inside diameter of curvature is about-6.25 inches. The slope of the spiral represents a drop'of about 3 inches per foot. While the trough is more or less semicircular in shape, the bottom thereof is slightly flattened. It is not necessary, however, that this shape be maintained in order to give satisfactory results. Spirals or so-called helical chute concentrators of this general type are commercially available. One suitable type of concentrator is described in United States Patent No. 2,431,560, issued to I. B.

Humphreys.

v In each turn of the spiral, there may be one or more drawotfs or ports,-with the exception of the first turn. These drawoffs or ports are positioned according to the fraction which it is desired to bleed off from each turn of the trough. In the separation of langbeinite from sylvite and halite, the langbeinite tends gradually to accumulate and to move in a path. approaching the inner edge of the spiral. The drawoffs, therefore, are displaced from the center line of the flattened bottom portion of the troughs and so positioned that generally the langbeinite component of the ore moving in the flow path will automatically fall into the drawoff.

By way of further explanation, the slurry of ore and brine courses through the. trough and the sylvite and halite efiect a gradual but substantial segregation from the langbeinite. In langbeinite separations, the langbeinite moving in brine as a'slurry follows'a, path of shortest diameter and the'substantially' nonagglomerated sylvite and halite particles plus brine move as slurry tending to move in its downward'flow to'the outside or large diameter wall of the trough. At the vdrawoifs, a predominantly langbeinite-brine slurry is withdrawn as the beneficiated ore fraction. At the lowest end of the spiral, a

' predominantly sylvite-halite brine slurry is recovered as various constituents. It may be desirable or economical the tailing. In their travel through the spiral, the solids are travelling in a stream of relatively shallow depth. Langbeinite ore apparently rides in the brine and shows substantially no agglomeration or clustering together of the particles. The sylvite and halite likewise can be observed to be moving as individual particles. The langbeinite in its flow through the spiral acquires a different velocity than the sylvite and halite. This velocity difference between ore components is dependent upon the factors of ore concentration, volume throughput, size of the spiral trough as governed by the outside diameter, and slope of the spiral.

The beneficiated langbeinite ore is delivered from the drawoff ports of the spiral and is either subjected to further beneficiating treatment by other processes or it may be further beneficiated by refeeding the concentrate to the same or another spiral, usually termed a cleaner spiral. Likewise, the tails or tailings which are delivered from the last turn of the spiral may be subjected to further treatment either by flotation, tabling or spiralling to recover my langbeinite values remaining therein.

As a further embodiment of the invention, it has been discovered that separations may also be attained by inclusion of one or more rifiles attached to the inner surface of the spiral trough. These elements may be of any desired height from the floor of the trough, but in general, good results are attained using a riflie having a height of between about 1 inch and about A inch. They are so positioned in the bottom of the trough that the langbeinite is conducted or directed to a drawotf port. In other words, the ruffle is obliquely positioned to found in commercial plants recovering potassium values from potash ores.

The temperature of the brine solution and the slurry is a further important feature of the invention. The temperature is, of course, at least above the freezing point of the brine and it is also preferable that the temperature be below about C. and still more preferably below about 30 C. At high temperatures, the rate of reaction of. the langbeinite with the brine is substantially more rapid, which would result in loss of langbeinite if higher temperatures were used.

In order to give a fuller understanding of the invention, but with no intention to be limited thereto, the

the path of flow of the pulp so as to direct the lang- I beinite material to the drawoff port, the sylvite and halite continuing on over the riffie relatively unaffected. It is contemplated that the invention may be practiced while employing any given number of riflles, depending, of course, upon the amount of sylvite and halite particles to be removed from the particular ore being processed.

The slurry of langbeinite concentrate recovered from the spiral separation operation is collected and is preferably rapidly treated so as to separate the langbeinite from the brine. A suitable method of accomplishing this is by collecting the slurry from the spiral concentrator on a screen of suitable mesh size to retain the langbeinite while permitting the water to pass through. Other separation methods for separating solids from liquids may, however, be used.

It has been determined that in order to obtain maximum recovery of langbeinite, the time interval from when the langbeinite material is pulped with brine to when the langbeinite concentrate is recovered from the lower end of the spiral and separated from the brine should be less than about five minutes and preferably less than about three and one-half minutes. This time limitation has been determined to be an important feature of this invention.

It has also been determined that the composition of the brine in which the langbeinite ore is slurried is important. The brine preferably has a high MgCl content. Specifically, it is preferable that the MgClcontent of the brine be at least 12% by weight. It is also preferred that the brine be acidulated with hydrochloric acid to give a pH within the range of from about 4.0 to about 6.8 and more preferably within the range of from about 4.5 to about 6.5. With the pH adjusted by the use of hydrochloric acid, it has been determined that losses of sylvite values in the ore by dissolving in the brine are considerably reduced. Accordingly, when maximum recovery of sylvite and haliae is desired, acidulated brine should be used. In a series of two tests, a brine was prepared by saturating a MgCl brine with mixed ore salts by three stages of mixed ore conditioning and decantation. In one of the tests, the Mgcl brine was acidulated to a pH of 5.7 through the addition hydrochloric acid. The head analysis of ore heneficiated using the non-acidulated brine showed that the KCl content was reduced from 14.6% KCl to 11.8% KCl, which indicated that KC] values were lost through solution of the KCl in the brine during processing. In a test using the acidulated brine, no apparent loss of KCl values by dissolving in the brine was noted. The brine preferably also has a high KCl and a high NaCl content and the brine is preferably saturated with respect to KC]. Brines having compositions of this nature are frequently following specific example is given.

Exam ple An ore assaying 28% langbeinite, 12% sylvite, and 52% halite was crushed and screened to produce a -14 mesh fraction. The ore was then slurried in a brine to about 24% solids. The brine, which was acidulated to a pH of 5.7 with hydrochloric acid, was at about 28 C. and had the following analysis:

Percent Na+ 0.87 M g++ 5 .70 SO 2.39 Cl" 22.03

The slurried ore was passed at the rate of 2.64 tons of solids/hr. into the top of a spiral trough about 6 ft. high, having 5 turns in the spiral, the outside diameter of the curvature of the spiral being about 24 inches and the inside diameter of the curvature of the spiral being about 6.25 inches. The slope of the spiral trough represented a drop of about 3 inches per foot. The crosssection of the trough was more or less semicircular in shape. At intervals along the bottom of the spiral trough, the langbeinite concentrate was removed through ports or drawoifs. These drawolfs were spaced about three per turn of the spiral, except the first turn. The sylvite-halite tailing was delivered from the last turn of the spiral. The langbeinite concentrate, denominated a rougher middling, was separately collected and then subjected to another spiral separation operation, denominated a cleaner operation. In this spiral separation operation a spiral of the same dimensions was used. A langbeinite concentrate cleaner was Withdrawn through the drawoff ports and the sylvite-halite cleaner tail was delivered from the last turn of the spiral. The langbeinite concentrate was rapidly separated from the solution, the Interval from the time the ore was slurried in brine to the time the cleaner langbeinite concentrate was separated from the brine 'being about two minutes. The results of this test are tabulated below in the table.

Percent Percent Percent Wt. Langbeinite Sylvite Halite Product Percent Assay Dis- Assay Dis- Assay Distribn tribn trlb'n Cltearger Concen- 2G 79 72 3 7 Not analyzed. ra e. Cleaner Tail 9 32 10 8 G Do. Rougher Middling. 12 30 13 10 10 D0.

The foregoing description of the invention utilizes specific reference to certain process details; however, it is to be understood that such details are illustrative only and not by way of limitation. Other modifications and equivalents of the invention will be apparent to those skilled in the art from the foregoing description.

Having now fully described and illustrated the invention, what is desired to be secured and claimed by Letters Patent is set forth in the appended claims.

1. A process of concentrating langbeinite in an ore containing langbeinite, sylvite and halite which comprises preparing a freely flowing aqueous pulp of sized ore by mixing sized ore with brine, flowing said pulp by gravity as a slurry stream in a spiral path at a rate of flow at least, suflicient to avoid any substantial amount of ag glor'neration' of particles, collecting a langbeinite concentrate portion from the spiralled stream as a slurry, and substantially separating the langbeinite concentrate from aqueous solution, the time interval from when the ore is mixed with brine to when the langbeinite concentrate is substantially separated from the aqueous solution being less than about five minutes. i

2. Aprocessof concentrating langbeinite in an ore containing langbeinite, sylvite and halite which comprises preparing a freely flowing aqueous pulp of sized ore by mixing sized ore having a particle size within the range of from about 8 mesh to about 100 mesh with brine, flowing said pulp by gravity as a slurry stream in a spiral path at a rate of flow at least suflicient to avoid any substantial amount of agglomeration of particles, collecting a langbeinite concentrate portion from the spiralled stream as a slurry, and substantially separating the langbeinite concentrate from aqueous solution, the time interval from when the ore is mixed with brine to when the langbeinite concentrate is substantially separated from the aqueous solution being less than about five minutes.

3. A process of concentrating langbeinite in an ore containing langbeinite, sylvite and halite which comprises preparing a freely flowing aqueous pulp of sized ore by mixing sized ore having a particle size within the range of from about 14 mesh to about 48 mesh with brine, flowing said pulp by gravity as a slurry stream in a spiral path at a rate of flow at least suflicient to avoid any substantial amount of agglomeration of particles, collecting a langbeinite concentrate portion from the spiralled stream as a slurry, and substantially separating the langbeinite concentrate fiom aqueous solution, the time interval from when the ore is mixed with brine to when the langbeinite concentrate is substantially separated from the aqueous solution being less than about five minutes.

4. A process of concentrating langbeinite in an ore containing langbeinite, sylvite and halite which comprises preparing a freely flowing aqueous pulp of sized ore by mixing sized ore having a particle size within the range of from about 14 mesh to about 48 mesh with brine having a high magnesium chloride concentration, flowing said pulp by gravity as a slurry stream in a spiral path at a rate of flow at least suflicient to avoid any substantial amount of agglomeration of particles, collecting a langbeinite concentrate portion from the spiralled stream as a slurry, and substantially separating the langbeinite concentrate from aqueous solution, the time interval from when the ore is mixed with brine to when the langbeinite concentrate is substantially separated from the aqueous solution being less than about three and one-half minutes.

5. A process of concentrating langbeinite in an ore containing langbeinite, sylvite and halite which comprises preparing a freely flowing aqueous pulp of sized ore by mixing sized ore having a particle size within the range from about 8 mesh to about 100 mesh with brine having a magnesium chloride content of at least 12% by weight and a temperature below about 35 C., flowing said pulp by gravity as a slurry stream in a spiral path at a rate of flow at least suflicient to avoid any substantial amount of agglomeration of particles, collecting a langbeinite concentrate portion from the spiralled stream as a slurry, and substantially separating the langbeinite concentrate from aqueous solution, the time interval from when the ore is mixed with brine to when the langbeinite concentrate is substantially separated from the aqueous solution being less than about five minutes.

6. A process of concentrating langbeinite in an ore pulp by gravity as a slurry stream in a spiral path at t containing langbeinite, sylvite and halite which comprises preparing a freely flowing aqueous pulp of sized ore by mixing sized ore with brine substantially saturated with respect to sylvite, having a magnesium chloride content of at least 12% by weight and at a temperature below about 35 C., flowing said pulp by gravity as a slurry stream in a spiral path at a rate of flow at least sufficient to avoid any substantial amount of agglomeration of particles, collecting a langbeiniteconcentrate portion from the spiralled stream as a slurry, and substantially separating the langbeinite concentrate from aqueous solution, the time interval from when the ,oreis mixed with brine to when the langbeinite concentrate is substantially separated from the aqueous solution being less than about three and one-half minutes. r. Y

7,. A process of concentrating langbeinite in an ore containing langbeinite, sylvite and halite which comprises preparing a freely flowing aqueous pulp of sized ore by mixing sized ore with brine substantially saturated with respect to sylvite, having a magnesium chloride content of at least 12% by weight and at a temperature below about 30 C., flowing said pulp by gravity as a slurry stream in a spiral path at a rate of flow at least suflicient to avoid any substantial amount of agglomeration of particles, collecting a langbeinite concentrate portion from the spiralled stream as a slurry, and substantially separating the langbeinite concentrate from aqueous solution, the time interval from when the ore is mixed with brine to when the langbeinite concentrate is substantially separated from the aqueous solution being less than about five minutes.

8. A process of concentrating langbeinite in an ore containing langbeinite, sylvite and halite which comprises preparing a freely flowing aqueous pulp of sized ore having a particle size within the range of from about 8 mesh to about mesh by mixing sized ore with brine substantially saturated with respect to sylvite, having a magnesium chloride content of at least 12% by weight and at a temperature below about 35 C., flowing said pulp by gravity as a slurry stream in a spiral path at a rate of flow at least sufiicient to avoid any substantial amount of agglomeration of particles, collecting a langbeinite concentrate portion from the spiralled stream as a slurry, and substantially separating the langbeinite concentrate from aqueous solution, the time interval from when the ore is mixed with brine to when the langbeinite concentrate is substantially separated from the aqueous solution being less than about five minutes.

9. A process of concentrating langbenite in an ore containing langbeinite, sylvite and halite which comprises preparing a freely flowing aqueous pulp of sized ore having a particle size within the range of from about 14 mesh to about 48 mesh by mixing sized ore with brine substantially saturated with respect to sylvite, having a magnesium chloride content of at least 12% by weight and at a temperature below about 30 C., flowing said a rate of flow at least suflicient to avoid any substantial amount of agglomeration of particles, collecting a langbeinite concentrate portion from the spiralled stream as a slurry, and substantially separating the langbeinite concentrate from aqueous solution, the time interval from when the ore is mixed with brine to when the langbeinite concentrate is substantially separated from the aqueous solution being less than about three and one-half minutes.

10. A process of concentrating'langbeinite in an ore containing langbeinite, sylvite and halite which comprises preparing a freely flowing aqueous pulp of similar sized ore by mixing sized ore having a particle size within the range of from about 14 mesh to about 48 mesh with brine substantially saturated with respect to sylvite and acidulated with hydrochloric acid to a pH within the range of from about 4.0 to about 6.8, and having a high magnesium chloride concentration, flowing said pulp by gravity as a slurry stream in a spiral path at a rate of flow at least sufficient to avoid any substantial amount of agglomeration of particles, collecting a langbeinite concentrate portion fromthe spiralled stream as a slurry, and substantially separating the'langbeinite concentrate from aqueous solution, the time interval from when the ore is mixed with brine to when the langbeinite concentrate is substantially separated from the aqueous solution being less than about three and one-half minutes.

ll. A process of concentrating langbeinite in an ore containing langbeinite, sylvite and halite which comprises preparing a freely flowing aqueous pulp of sized ore having a particle size within the range of from about 14 mesh to about 48 mesh by mixing sized ore with brine substantially saturated with respect to sylvite, and acidulated with hydrochloric acid to a pH within the range from about 4.5 to about 6.5, and having a mag nesium chloride content of at least 12% by weight and ore is mixed with brine to when the langbeinite concentrate is substantially separated from the aqueous solu 10 tion being less than about three and one-half minutes.

References Cited in the file of this patent UNITED STATES PATENTS 15 2,431,559 Humphrcys Nov. 25, 1947 2,733,809 Wrege et al. "Feb. 7, 1956'- 2,783,886

Le Baron Mar. 5,-1957 

1. A PROCESS OF CONCENTRATING LANGBEINITE IN AN ORE CONTAINING LANGBEINITE, SYLVITE AND HALITE WHICH COMPRISES PREPARING A FREELY FLOWING AQUEOUS PULP OF SIZED ORE BY MIXING SIZED ORE WITH BRINE, FLOWING AQUEOUS PULP BY GRAVITY AS A SLURRY STREAM IN A SPIRAL PATH AT A RATE OF FLOW AT LEAST SUFFICIENT TO AVOID ANY SUBSTANTIAL AMOUNT OF AGGLOMERATION OF PARTICLES, COLLECTING A LANGBEINITE CONCENTRATE PORTION FROM THE SPIRALLED STREAM AS A SLURRY, AND SUBSTANTIALLY SEPARATING THE LANGEBEINITE CONCENTRATE FROM AQUEOUS SOLUTION, THE TIME INTERVAL FROM WHEN THE ORE IS MIXED WITH BRINE TO WHEN THE LANGBEINITE CONCENTRATE IS SUBSTANTIALLY SEPARATED FROM THE AQUEOUS SOLUTION BEING LESS THAN ABOUT FIVE MINUTES. 